This proposal examines the pathway by which insulin regulates GLUT4 translocation in adipocytes. The P.I. has devised a novel method that will enable him to study the cycling of GLUT4 in these cells. Specific aims are (1) to kinetically characterize the insulin-regulated trafficking pathway. This will be done by measuring the rate constants of endocytosis and recycling, both in the presence and absence of insulin. (2) To characterize the intracellular compartments of the insulin-regulated trafficking pathway using quantitative fluorescence microscopy. The relationship with the general recycling pathway will be determined. (3) To identify the proteins of the insulin-regulated recycling compartment using HRP ablation. Novel IRC proteins will be identified. (4) To identify the trafficking motifs of the cytoplasmic domains of vp165.